This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
One problem in wireless ad hoc networks relates to the synchronization from node to node due to each node transmitting its synchronization message during its beacon period. During these beacon periods, other node's receivers have to be kept on. During a node's own beacon period, there may be a number of collisions in a dense multi-hop environment when multiple nodes attempt to send their own synchronization message.
The following abbreviations that may be found in the specification and/or drawing figures are defined as follows:
CRcognitive radioState NREnode readyState NRXnode receivingState NTXnode transmittingSub state BEbeacon (node is either transmitting or receiving depending on the node's state)Sub state MImissed (node has not been able to receive the messagesynchronization correctly)Sub state NOnothing (no synchronization message has been found)Sub state REready (the beacon period has finalized successfully)Pupdateperiod update (change the length of the next transmission period)MiRxFRmissed frame (a running count of missed frames per transmission period)TxPeriodlength of a transmission period
In one mode of wireless local area network (WLAN) systems, the communicating nodes contend with one another for transmissions in the beacon period (e.g. 100 ms) regarding the sharing of network resources. This represents an ad hoc network since there is no hierarchy of nodes in which one node controls/allocates radio resources. Further, implementations of WLAN may suffer from an inability to be effectively scaled.
Significant research has been invested in the context of a cognitive radio network in response to this problem. Cognitive radio is also an ad hoc environment in which nodes opportunistically find spectrum holes which are not scheduled by a controlling entity. A considerable amount of effort in cognitive radio development has been directed to achieving non-interfering coexistence, such as with existing cellular wireless communication systems where they might find those spectrum holes. Scaling ad hoc networks for high densities of users remains a challenge.
As such, there is a need for techniques to scale ad hoc systems to high user densities, as for example in a case where there may be a large number of personal wireless devices with wireless connectivity. Such techniques should not impose a high power demand on those wireless nodes.